A fused toner image is an image formed by toner particles that are melted by heating so as to adhere to the media substrate. Gloss is related to a quantity of light reflectance that can be measured with a gloss meter. Gloss may be controlled by selecting a defined fusing temperature, with higher fusing temperatures, giving higher gloss and lower fusing temperatures giving lower gloss. The amount of gloss enhancement with the conventional fuser temperature control method, however, is limited. Moreover, adjustable gloss between various parts of the image is not possible, as the entire image must be heated uniformly by the fuser.
In high-speed, high-quality electrophotographic printing applications, it may be desirable to get higher gloss on, for example, the pictorial areas as compared to the text areas. This may be achieved by selectively applying a gloss enhancing toner on the pictorial areas, as disclosed by Ng in U.S. Pat. No. 5,234,783, herein incorporated in its entirety by reference.
However, in order to gloss-up (that is, increase the gloss of the finished printed image) the pictorial areas, a low viscosity (e.g., about 1300 poise) gloss enhancing toner must be used. There are limitations in the amount of gloss enhancing toner that may be selectively laid-down based on fuser temperature, nip width, and the like. Consequently, there are limitations in the amount of gloss enhancement that may be achieved with conventional methods. Further, by using a low viscosity gloss enhancing toner, the image relief may increase to unacceptable levels and differential gloss, for example, within the pictorial area, may also be at a level (e.g., >30) too high to be acceptable to the end user.
As can be seen, there is a need for improved adjustable gloss control between different sections of a single printed page.